<p></p>
<p><b>@AntonKhorev</b> commented on this pull request.</p>

<hr>

<p>In <a href="https://github.com/openstreetmap/openstreetmap-website/pull/5826#discussion_r2004515398">app/assets/javascripts/index/history.js</a>:</p>
<pre style='color:#555'>> +    changesetIntersectionObserver = new IntersectionObserver((entries) => {
+      if (ignoreIntersectionEvents) {
+        ignoreIntersectionEvents = false;
+        return;
+      }
+
+      let closestTargetToTop,
+          closestDistanceToTop = Infinity,
+          closestTargetToBottom,
+          closestDistanceToBottom = Infinity;
+
+      for (const entry of entries) {
+        if (entry.isIntersecting) continue;
+
+        const distanceToTop = entry.rootBounds.top - entry.boundingClientRect.bottom;
+        const distanceToBottom = entry.boundingClientRect.top - entry.rootBounds.bottom;
+        if (distanceToTop >= 0 && distanceToTop < closestDistanceToTop) {
+          closestDistanceToTop = distanceToTop;
+          closestTargetToTop = entry.target;
+        }
+        if (distanceToBottom >= 0 && distanceToBottom <= closestDistanceToBottom) {
+          closestDistanceToBottom = distanceToBottom;
+          closestTargetToBottom = entry.target;
+        }
+      }
+
+      if (closestTargetToTop && closestDistanceToTop < closestDistanceToBottom) {
+        const id = $(closestTargetToTop).data("changeset")?.id;
+        if (id) {
+          OSM.router.replace(location.pathname + "?" + new URLSearchParams({ before: id }) + location.hash);
+        }
+      } else if (closestTargetToBottom) {
+        const id = $(closestTargetToBottom).data("changeset")?.id;
+        if (id) {
+          OSM.router.replace(location.pathname + "?" + new URLSearchParams({ after: id }) + location.hash);
+        }
+      }
+    }, { root: $("#sidebar")[0] });
</pre>
<p dir="auto">Every time as opposed to what? Are you proposing to reuse one callback when creating new observers?</p>

<p style="font-size:small;-webkit-text-size-adjust:none;color:#666;">—<br />Reply to this email directly, <a href="https://github.com/openstreetmap/openstreetmap-website/pull/5826#discussion_r2004515398">view it on GitHub</a>, or <a href="https://github.com/notifications/unsubscribe-auth/AAK2OLOOUZJP7XR524J3WH32VIBKVAVCNFSM6AAAAABZMDKPQCVHI2DSMVQWIX3LMV43YUDVNRWFEZLROVSXG5CSMV3GSZLXHMZDOMBQGYZDENRXHA">unsubscribe</a>.<br />You are receiving this because you are subscribed to this thread.<img src="https://github.com/notifications/beacon/AAK2OLMCCIBREPGD6KFTVW32VIBKVA5CNFSM6AAAAABZMDKPQCWGG33NNVSW45C7OR4XAZNRKB2WY3CSMVYXKZLTORJGK5TJMV32UY3PNVWWK3TUL5UWJTVA7A5VM.gif" height="1" width="1" alt="" /><span style="color: transparent; font-size: 0; display: none; visibility: hidden; overflow: hidden; opacity: 0; width: 0; height: 0; max-width: 0; max-height: 0; mso-hide: all">Message ID: <span><openstreetmap/openstreetmap-website/pull/5826/review/2700622678</span><span>@</span><span>github</span><span>.</span><span>com></span></span></p>
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